巢湖沿岸圩区稻季营养盐的输出特征研究

巢湖流域沿岸分布着很多圩区,人们在圩内进行各种农业活动,圩区营养盐的输出是造成巢湖流域非点源污染的重要因素。为了解圩区农业非点源营养盐的输出特征,笔者通过在巢湖流域河网地区选择比较典型的圩区,于2014年水稻生长期进行了较系统的野外调查观测、取样和室内水质分析,探讨在自然降雨-径流的条件下圩区各类营养盐的浓度变化及输出特征。2014年稻季共进行了9次排水,排水量总计73.09 mm,径流系数为0.37,9次排水事件总氮(TN)和总磷(TP)的平均浓度分别是3.42、0.22 mg/L,圩区水体处于富营养化水平。降雨-径流强度是影响营养盐浓度变化的重要因素,稻季生长期内TN和TP的输出量是0.28、0.017 kg/hm2,占稻季施肥总量的1.7%和0.16%。径流量是影响营养盐输出总量的关键因素,同时施肥量和施肥至排水事件的间隔天数也是是影响营养盐输出的重要因素。

Study on Nutritive Salt Export Characteristics From Polder Areas Around Chao Lake During Rice Season

There are many polder areas located around Chao Lake and agricultural activities are conducted in these areas. Nutritive salt exportation from polder areas is an important factor of non-point source pollution in Chao Lake. In order to understand nutritive salt export characteristics in this area, a typical polder area located on the coast of the lake was chosen for the study, systematic field survey observation, sampling and indoor water quality analysis were conducted in rice growing period in 2014, and the change of concentration and export characteristic of nutritive salt in polder areas under natural rainfall-runoff condition were discussed. There were 9 rainfall-runoff events in rice season in 2014 and the total amount was 73.09 mm, runoff coefficient was 0.37. The mean concentration of total nitrogen (TN) and total phosphorus (TP) were 3.42 and 0.22 mg/L in the 9 rainfall-runoff events, which reached the eutrophication levels. The amount of drainage played an important role in the variation of nutritive salt concentration, the export amount of TN and TP in rice growing period were 0.28 and 0.017 kg/hm², which accounted for 1.7% and 0.16% of nitrogen and phosphorus fertilization input. Volume of runoff was also an important factor of nutritive salt export, meanwhile, fertilizing amount and the interval between fertilization and rainfall-runoff events could affect nutritive salt exportation.